Fix Open WebUI iOS backgrounding frozen-chat bug

Job description

Source issue: https://github.com/open webui/open webui/issues/26844 Bug summary: On iOS Safari, if Open WebUI is backgrounded immediately after sending a chat and then reopened after the response finishes, the conversation can remain stuck in a loading state until the page is refreshed. The completed response exists server side, so this appears to be a client side resume / reconnection state bug. Scope: Reproduce the mobile backgrounding issue described in the GitHub issue. Identify the client side root cause around resume, websocket loss, or state refresh after returning from background. Implement a fix so completed chat state is restored when returning to the app. Verify behavior on the affected mobile flow. Acceptance criteria: Returning to Open WebUI after backgrounding no longer leaves the chat stuck loading. The completed response becomes visible without requiring a manual refresh. Include a short implementation note with root cause, files changed, and verification steps. Prefer a PR ready patch or clean change set. Tech context: Likely fits TypeScript / React / mobile web state management debugging work.